Self-locking plug



g- 6, 1940' A. L. KUHLM'AN' 1 25 SELF-LOCKING PLUG Filed March 23, 1938 fm/L/mr 8- 70 g -.z a

INVENTOR.

ATTORNEY.

Patented Aug. 6,1940

UNITED STATES PATENT OFFICE Application March 23,

7 Claims.

This invention relates to electric plugs such as :used to. electrically connect toasters, electric irons, lamps, and similar electrical equipment and appliances with a source of electrical current.

One of the prime objects of the invention is to design a self-locking plug which will be automatically locked against accidental or unintentional removal when it is .plugged into position to establish electrical connection of an electrical appliance with a source of electric current.

Another object is to design a self-locking plug which is simple and inexpensive to manufacture and assemble, and which is composed of few parts, all of sturdy and substantial construction.

A further object is to provide a,self-locking plug including resilient'prong members, and provide means on the prongs for firmly locking them in contact in a socket.

A still further object is to provide a yieldable plug body having an insulator member mounted therein and to which the electrical conductors are connected in such manner as to prevent disconnection occasioned by accidental pulls or jerks.

This invention possesses other objects and features of advantage, some of which, together with the foregoing will be set forth in the following description of the preferred form of the invention which is illustrated in the accompanying drawing which forms part of the specification; it being understood however, that changes may be made in the form, size, proportion and'minor detailsof construction, without departing from the spirit, or sacrificing any of the advantages of the invention.

In the drawing- Fig. 1 is a perspective front view of an electrical receptacle showing my self-locking plug connected therewith.

Fig. 2 is an enlarged vertical sectional view through the plug, the broken lines showing the prongs sprung inwardly to permit removal from the socket.

Fig. 3 is a perspective view of the insulator block.

Fig. 4 is an enlarged detail of one of the prongs.

Referring now more specifically to the drawing in which I have shown one embodiment of my invention, the numeral 8 indicates the yieldable plug body. This is formed of live rubber suitably moulded to the shape desired and is formed with oppositely disposed thumb and finger rests 9 which are raised slightly above the main body, and for a purpose to be presently described.

A centrally disposed passage I is moulded in the upper end of the plug body and opens into 1938, Serial No. 197,546 (Cl. 173-361) angular in cross section'and spaced apart open- 10 ings "Send I! respectively are provided therein, said section being preferably angular in cross section so that it snugly flts' the face and edge of the insulator block, the openings l6 and "being in alignment with similar openings l9 and 20 provided in said block, the opening being threaded to accommodate the screw 2| which forms a binding post, and to which the end of one of the conductors I4 is anchored in the usual manner.

The leg section of the prongs is bent over and around to form a loop 22, the lower section extending downwardly and projecting beyondthe face of the plug, a shoulder 23 being provided on the leg intermediate its length, and this shoulder is adapted to engage the shell of the receptacle C to firmly hold the prongs in locked engagement therewith.

I wish to direct particular attention 'to the manner of attaching the electrical conductors to the insulator block, the conductors leading along the opposite faces 01' the block, thence being threaded through the openings l9, and thence leading up-' wardly and being anchored to the threaded screw or post 2| in the usual manner, each conductor being secured in an identically similar manner, and it will be obvious that any jerk or severe pull will be taken by the insulator block, and there will be less tendency to pull the wire from the binding post or screw 2| and break the connection, the ribs I3 serving to keep the conductor wires in proper position.

It will be understood that the hollow portion of the plug is shaped to snugly fit the insulator block and the bowed prongs, suflicient clearance being provided to permit the bowed sections to be sprung when releasing the plug.

In practise the plug is inserted in a suitable receptacle or socket in the usual manner, the shoulders 23 engaging the receptacle shell and firmly locking it in position, then when it is desired to release, the user places the thumb and forefinger on the rests 9, squeezing the plug and flexing the looped sections 22 of the prongs so that they assume position as shown in broken stantial, there are no intricate or delicateparts,

the connections are sturdy and secure,v and it can be easily manufactured and assembled. 7

From the foregoing description, it will be obvious that I have perfected a very simple,

self-locking plug for electrically connecting electrical appliances with an electric current. What I claim is:

l. A self-locking plug of the character described comprising a hollow, yieldable body porjj tion, a rigid insulator block mounted in said hollow body, resilient prongs mounted in, said plug body portion with their free ends-projecting beyond the face of said plug body portion, the inner" end sections of said prongs being shaped toiorm i an open loop with the ends secured to said in-.-

sulator block to permit said prongs to be sprung toward each other when pressure is exerted on the side walls of the resilient body portion to spring said loop sections inwardly and force the free ends of the prongs toward each other, shoulders on the free ends of the prongs and adapted to releasably engage the said wall of a receptacle, and electrical conductors connected to said prongs. I

2. The combination as set forth in claim 1 in which the inner end of each prong is iormed with a turned flat section of relatively large area -for attachment to said insulator block.

3. The combination as set forth in claim 1 in which the insulator block is formed with cored openings so that each conductor extends through one of said cored openings before being connected to one of said prongs.

4. A self-locking plug of comprising a hollow, yieldable body portion,aninsulating block mounted in said hollow body porthe class described,

tion, resilient prongs mounted on said block with the free ends projecting beyond the face of the body portion, the inner end sections of the prongs being shaped to form an open loop snugly fitting in said hollow portion and permitting said prongs to be sprung toward each other when pressure is exerted at predetermined points on the side walls of the resilient body portion tospring said loop sections inwardly, shoulders on the project ing free ends of the prongs directly adjacent the end of the body portion and adapted to engage the'end wall of the shell of a receptacle when the .plug is inserted in a receptacle, and electrical conductors secured to the oppositesides of said block.

5. The combination set forthin claim 4, which includes raised thumb and finger rests formed integral with saidfbody portion in horizontal alignmentwiththe looped sections of the prongs.

6. The combination as defined in claim 4 in which the hollow porticnof the plug is shaped to accommodate the "insulator bloclg and looped portions of theprongs, and permit the looped sections to be sprung to release the shouldered sections of the prongs from a receptacle when presure is exerted on the yieldable body.

7. A self-locking plug of the class described, comprising a one piece, hollow, yieldable. body portion havingacentrally disposed cored openings therein, an insulator block mounted in said hollow body portion, one piece prongs mounted on,

said block with their lower ends projecting beyond the face of the body portion, a shoulder on the projecting end of each prong directly adjacent the face of the, body portion, the upper and sections being shaped to form an open loop to permit said prongsto be forced towards each other when pressure is exerted onthe yieldable body portion and the looped portions of the prongs, and electrical conductors leading through said coredopening and connected to said prongs.

. ARTHUR L. KUHLMAN. 

